Solar Information

"Off-Grid" refers to a solar system that is independent (not connected to) the electrical grid. Off-grid systems use batteries to store the power generated, so that the system functions even when the sun is not shining.

"On-grid" refers to a solar system that is connected to the electrical grid. On-grid systems can use power from the grid when the sun is not shining, and can feed excess power back into the grid when the sun is shining.

The first step to planning any solar system is to calculate the load that it will be expected to bear. This is done by making a list of the electronics that will be used, multiplying each one by the number of hours it will be used each day, and adding the totals together.

Calculation Example For "Load" (Watts Needed):
1 Computer (200W) For 3hrs/Day = 600W
1 Refrigerator (800W) For 24hrs/Day = 19200W
6×15W CFL Lamps For 3hrs/Day = 270W
Total = 20070W

Factor For Rainy Days:
1 Rainy Day = 1.1
2 Rainy Days = 1.2
3 Rainy Days = 1.3
4 Rainy Days = 1.4

Solar Power Formula #1:
(Load × Factor For Rainy Days) / (Hours of Bright or Direct Sunlight × 0.8 (Solar Panel Factor) × 0.9 (Inverter Factor))
Example: (20070W × 1.2) / (4 × 0.8 × 0.9) = (24084W / 2.88) = 8362.5W

Solar Power Formula #2:
(Load × Working Hours) / (1.8 × Hours of Bright or Direct Sunlight)
Example: (20070W × 3) / (1.8 × 4) = (60210W / 7.2) = 8362.5W

Both formulas produce the same result, so using the example above you will know that 34×250W solar panels, along with batteries, inverter, and controller that can handle the load (plus additional cables, brackets, etc.), will produce an off-grid system that will meet your requirements.


Solar Power Calculator:

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